Alien Hand Syndrome was first identified in 1909 and there have only been 40 to 50 recorded cases since. It wasn't clearly defined by doctors until 1972. It's believed that other instances may have been misdiagnosed as part of an existing mental health disorder. The rarity and non-threatening nature of Alien Hand Syndrome has led to infrequent research and a lack of hard data, resulting in a condition that's largely mysterious.